Disposable masks have been manufactured for many years. In the medical field, most of these masks have been for use in preventing contamination of a patient by the breath of healthcare personnel. In recent years with increased concern for infection of healthcare personnel with airborne pathogens, such as the hepatitis B virus, it has become necessary to prevent not only the contamination of patients due to exhalation from healthcare personnel, but also to prevent infection of healthcare personnel due to inhalation of airborne infection particles. It has become even more important in view of the advent of human immunodeficiency virus (HIV) and the recent increase in infectious tuberculosis associated with many HIV patients.
In addition, it has been found that aerosols having airborne liquid and solid particles are generated not only by the exhalation of infected patients, but also by certain procedural manipulations and processes that impart energy to any microbial suspension. Surgical procedures involving use of drills and saws are particularly prolific producers of the aerosols which may contain tuberculosis, HIV or other pathogens from an infected patient. Concern with tuberculosis has been increasing since new strains of the disease show strong resistances to multiple types of drug treatment.
In addition, it has been shown that many of the viral hemorrhagic fevers such as yellow fever, Rift Valley fever and perhaps Rocky Mountain spotted fever, rabies and smallpox can be transmitted through aerosols. A considerable number of studies have been made which are now beginning to identify the transmission of such viruses through "non-accident" situations. Accordingly, it is now believed that many of those "non-accident" situations result from aerosol contamination.
Of the current medical masks on the market, it appears that many are not effective against aerosols. One of the presently available molded-type surgical masks has almost no resistance to particles smaller than 2 microns and has a low efficiency in blocking particles as large as 9 microns. Some masks apparently demonstrate somewhat better qualities, but none appeared to be fully satisfactory in preventing the passage of aerosols through the mask or around the periphery of the mask.
One type of mask is illustrated in U.S. Pat. No. 2,012,505 issued on Aug. 27, 1935 to S. J. Goldsmith. Another type of disposable face mask is illustrated in U.S. Pat. No. 4,319,567. This mask is molded and has been especially configured in an effort to avoid the leakage of the flow of gases past the edges of the mask. Obviously, leakage cannot be tolerated when attempting to control aerosols. U.S. Pat. No. 4,606,341 issued Aug. 19, 1986 to Vance M. Hubbard and Welton K. Brunson shows a conventional rectangular face mask having a trapezoidal pleat. Rectangularly shaped masks, including the mask shown in patent '341, have less than the optimal fit to prevent the passage of aerosols between the periphery of the masks and a wearer's face. An additional folded type mask is illustrated in U.S. Pat. No. 4,688,566 issued Aug. 25, 1987 to Elvin L. Boyce. This patent illustrates another attempt to prevent the flow of fluids past the edges of a mask.
Therefore, a need has arisen for a mask which will prevent the passage of aerosols through the mask and maintain the ability of the mask to provide a sufficiently low pressure drop so that the wearer can breathe comfortably. A further need has arisen for a mask to seal totally around the periphery of the mask to prevent bypass of aerosols between the edges of the mask and the face of a wearer.